Method and apparatus for supervising casting of steel tubes

ABSTRACT

Method and equipment for supervising the continuous casting of steel tubes is disclosed. The tubes are water cooled as they leave the die and the steam pressure is used as an indicator for the forming of cracks to control retarding or stopping of the casting process at an early stage of crack forming.

United States Patent m1 3,593,773

[72] Inventors Gerd VOgt {51] lnt.Cl .B22d 13/10 Krefeld; [50]FieldofSearch. l64/4,85,

Josef Glaser, Gelsenkirchen; Manfred Strohschein. Gelsenkirchen;Johannes Kurth, Gelsenkirchen; Rudolf Schwitzgobel, Gelsenkirchen, allof. Germany 1 2| Appl. No. 830,296

{22] Filed June 4,1969

[45] Patented July 20, 1971 [73] Assignee Mannesmann AktiengesellschaftDusseldorf, Germany [32] Priority June 7, 1968 [33] Germany [54] METHODAND APPARATUS FOR SUPERVISING CASTING OF STEEL TUBES l 1 Claims, 2Drawing Figs. [52] US. Cl. 164/4, 164/154, 65/86, 65/16] 65/190, 65/191150, I51, I52, I53, 281, I54; 264/40, 173, 209; 122/504; 65/29. 86,1611, I87, I88, 189, 190, l9l,

[56] References Cited UNITED STATES PATENTS 2,145,438 l/l939 Thulin164/152 2,853,754 9/1958 Paddock... 164/85 3,327,761 6/1967 Rowell122/504 X Primary Examiner-J. Spencer Overlholser AssistantExaminer-John S. Brown Attorney-Smyth, Roston & Pavitt ABSTRACT: Methodand equipment for supervising the continuous casting of steel tubes isdisclosed. The tubes are water cooled as they leave the die and thesteam pressure is used as an indicator for the forming of cracks tocontrol retarding or stopping of the casting process at an early stageof crack formmg.

METHOD AND APPARATUS FOR SUPERVISING CASTING OF STEEL TUBES The presentinvention relates to a method and equipment for improving the continuouscasting of steel tubes which are cooled from the interior by sprayingwater onto the inner surface of a tube when leaving the die, and moreparticularly the invention relates to supervision of such castingprocess.

During continuous casting, the rods or tubes, as the case may be, areonly partially solidified as they leave the die. In fact, there isbarely a solid shell or mantle while the interior is still liquidous.The solid portion grows in thickness with increasing distance of tubingfrom the die, but even at an appreciable distancefrom the die theinterior of the tube walls, or even more so the interior of a rod, isstill in the liquid state. The cross-sectional dimension of this liquidcore decreases until the entire tube or rod has solidified remote fromthe die. It is now possible, however, that the already solidifiedportion of the tube or rod cracks and that some of the still liquidousin terior core pours out and over tube, die and other casting equipment.It is needless to say that should such cracking occur, it interruptsoperation and renders considerable portions of the cast tube or rodunusable.

Aside from the danger to equipment and product resulting directly fromthe outflow of liquid steel the employment ofinterior water coolingequipment for causing water to be sprayed upon the interior surface of acast tube, establishes an additional source of considerable danger,particularly for the personnel. As the tube cracks and liquidous steelpours through the crack the amount of water vapor and steam developed issuddenly increased. The pressure in the tube increases accordingly, andmay well lead to explosion. Unfortunately, it is yet unknown how torecognize the initial conditions leading to the formation of suchcracks, sufficiently early to positively prevent at all any cracking ofthe cast product prior to its complete solidification. Such cracksdevelop too sudden and under basically unforeseen circumstances.

It is an object of the present invention to establish method andequipment for continuously casting of steel tubes in which at least theproduction of a crack in the interior of a tube is recognized in thedeveloping stage, i.e., sufficiently early so that continued developmentof the crack and enlargement thereof can be at least materially impeded.

In accordance with the preferred embodiment of the invention, it issuggested to continuously measure the steam pressure in the interior ofa cast and to control the casting process in accordance with thatpressure. It was found to be of particular advantage to measure thevapor pressure directly in the region of spraying within the tube. Itwas found in particular that for a constant rate of flow of spray waterthe steam pressure increases drastically as soon as a crack begins toform in the interior wall surface of the tube. Such a crack in theinterior of the tube exposes still hot portions of the solidifiedportion of the tube closer to the still liquidous core in the tube wall,and even exposes liquid steel to the spray water. As soon as a crackbegins to form, liquid steel begins to seep into and through the crack.As a consequence, the rate of vaporization of spray water increasesrapidly as compared with undisturbed operation.

Sudden and steep increase of the water vapor pressure is, therefore, acertain sign for the creation ofa crack and which, if not stopped, couldpossibly lead to a complete breakage in the tube. In accordance with theincrease in vapor pressure, for example, the casting process is changed.For example, the flow or metal into the die is throttled as soon as thewater vapor pressure increases. Moreover, in case a particular thresholdpressure has been reached, and/or in case the rate of pressure increaseis steep and persistent, it is advisable to interrupt the castingprocess completely. Additionally, the flow of water to be sprayed issubject to control in accordance with the current steam pressure. Excesspressure will result in a complete throttling of the supply to preventexplosion.

It was found that with aid of the inventive method it is actuallypossible to monitor the beginning of the formation of a crack in theinterior of'the tube at such an early state that by appropriate andspeedy control an enlargement of that crack can be prevented. Moreover,the early detection permits taking of adequate measures against anycatastrophic effects of an outpour of liquid steel through a large crackand even against the outpour itself by speedily impeding the formationof a large crack. The casting of a tube is intended as an illustrativeexample. The invention will find utility for continuously casting ofhollow objects with internal cooling.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention, it is believed that the invention, the objects and featuresof the invention and further objects, features and advantages thereofwill be better understood from the following description taken inconnection with the accompanying drawings in which;

FIG. i there is illustrated somewhat schematically a cross sectionthrough a continuous casting equipment for the casting of steel tubes;and

FIG. 2 illustrates a modification of the equipment shown in FIG. ll.

The equipment illustrated in FIG. ll includes a water-cooled die memberI having a die cavity which actually has ringshaped configuration;because a water-cooled, hollow mandrel 2 projects centrally into the diecavity. Liquid steel is fed into the die from a container or hopper 111having an aperture Ila which can be closed by a movable plug or stopperelement 10. A continuous hollow product, i.e., a cast tube 3 leaves thebottom die, i.e., the steel normally continuously pouring from hopper 11into die 11 leaves the bottom thereof as a formed tube 3.

Tube 3 when directly leaving the die is only partially solidified byoperation of the cooling process involving die and mandrel. Inparticular, the tube has initially very thin solid wall portions 312;there is an inner wall portion forming a thin tube and circumscribingthe hollow interior of tube 3 and there is an outer wall portion alsoforming a thin tube. These two wall portions 3b are separated by anessentially ringshaped liquid core 3a. At greater distance from the die,core 3a is reduced in cross-sectional dimension and vanishes when innerand outer portions 3b merge at large distance from the die.

It is conventional to spray water upon the outer surface of the tube toincrease rapidly the thickness of its solidifying outer wall portion.Equipment for spraying water on the outer tube surface is now shown andis not considered to be a part of the invention. Also, it isconventional to provide rollers for the transporting the formed tubeaway from the die; as this is likewise known and does not constitute apart of the invention these rolls are, therefore, likewise notillustrated in detail.

The interior wall of the tube, particularly the inner surface of thecylindrical cavity defined by the tube is cooled by continuouslyspraying water through nozzles 5. Water is fed to nozzles 5 through apipe 4 which traverses the hollow mandrel 2 and is'under control ofavalve 112 for controlling the amount of water supplied to the nozzles.The water is directly sprayed onto the hot inner surface of the tube andpartially vaporizes. Water vapor thus produced escapes from the interiorof tube 3 through the hollow flow space of mandrel 2 communicating onone end with tube 3 and being on the other end connected to a steam pipe6. A suction device 7 sucks steam from pipe 6 to be discharged in thesurrounding atmosphere.

A measuring or sensing pipe 8 likewise traverses the hollow space ofmandrel 2 and extends down into the region where the tube 3 leaves thedie. The pipe 3 opens particularly to the zone adjacent the innersurface of the tube upon which coolant is sprayed. Measuring and probingpipe 8 is connected to a pressure measuring instrument It outside of thesteam zone. In lieu of employing the special measuring pipe 8, pressureinstrument 9 could also be connected directly to the pipe 6 for purposesof monitoring the pressure therein as representation of the pressure inthe interior of mandrel 2 and in the space defined by the interior oftube 3.

During normal operation and for a constant rate of water flow as passingthrough pipe 4 and nozzles 5 for spraying, instrument 9 will indicate aconstant value. The value is particularly determined by the rate ofspray water flow and by the relative low pressure in pipe 6. Should thepressure increase suddenly, instrument 9 will respond immediately. lfthe casting process itself did not change, nor was there any change inthe flow of cooling and spray water then such pressure increase clearlyrepresents that a crack is about to form and is in the initial state offormation. After the pressure increase has been detected, the castingprocess is changed so that further increase of a crack is impeded. Suchan impediment can be produced in a controlled manner as follows:

For example, the pressure in the spray zone as monitored by probing pipe8 acts upon an adjusting piston 13. It may be advisable to interpose,for example, a fluid amplifier in the connection path between probingpipe 8 and adjusting element 13. This way the control can be conductedat a particular characteristic as to when steel flow from hopper 11 isto be interrupted. The piston 13 may normally be in retracted positionbut is then actuated as a result of an increase in pressure of probingpipe 8. Piston l3 actuates a lever 14 which in turn moves stopper towarda more closing position.

Normally, the lever 14 is balanced by a weight 15 such that the stopper10 is retracted from hopper opening 11a so that casting proceeds at aparticular speed and rate of steel flow. Should the pressure in pipe 8exceed a particular value causing piston 13 to be actuated, stopper 10drops and the steel supply is diminished or even interrupted.

A similar arrangement could possibly be provided for the control of thespray water flow. As shown in FIG. 2, a pressure responsive transducer23 is connected to probe 8 responding to the pressure therein operatinga control box 24 which in turn causes valve 12 to throttle the amount ofwater in case the steam pressure increases. If a threshold pressurevalue is exceeded, the spray water flow is turned off completely.

The invention is not limited to the embodiments described above but allchanges and modifications thereof not constituting departures from thespirit and scope of the invention are intended to be included.

lclaim:

1. A method of supervising the continuous casting of steel tubes whichare cooled in the interior during casting by spraying of watercomprising the steps of:

measuring the pressure of the steam resulting from vaporization of thesprayed water, and

controlling the casting process in accordance with that pressure.

2. The method as set forth in claim 1 the control step includingthrottling of the water supply for spraying, upon sudden increase of thepressure.

3. The method as set forth in claim 1 the control of the casting processincluding the step of controlling the supply of liquid steel for thecasting process.

4. Apparatus for supervising the continuous casting of steel tubes whichincludes means for cooling the cast tubes in the respective interior byspraying of water, comprising:

means for measuring the pressure of the steam resulting fromvaporization of the sprayed water; and

means for controlling the casting process in accordance with thatpressure.

5. Apparatus as set forth in claim 4, the means for measuring includinga probing pipe extending into the interior of the cast tube.

6. Apparatus as set forth in claim 5, the probing pipe extending to aregion adjacent an interior surface portion of the cast tube towardswhich water is sprayed.

7. In an apparatus for continuously casting a steel tube, the cast tubeleaving a die cavity, there being means in communication with theinterior of the cast tube during the casting process;

the apparatus further including means for spraying cooling water ontothe inner surface of the cast tube, the improvement comprising:

first means in communication with the interior of the cast tube to beresponsive to the pressure of developing steam in the tube; and

second means operatively connected to the first means to retard thecasting process in response to development of pressure indicative ofacrack forming in the tube.

8. In an apparatus as set forth in claim 7 the second means includingmeans for controlling the flow of liquid steel into the die cavity.

9. in an apparatus as set forth in claim 8, the means included in thesecond means stopping flow of liquid steel into the die cavity when thesteam pressure exceeds a particular value.

10. In an apparatus as set forth in claim 7 including third meansconnected to the first means and responsive to the pressure in the tubeto control the flow of water for spraying the interior of the tube.

11. In an apparatus as set forth in claim l0 the third means throttlingthe flow of spray water when the pressure exceeds a danger limit.

1. A method of supervising the continuous casting of steel tubes whichare cooled in the interior during casting by spraying of watercomprising the steps of: measuring the pressure of the steam resultingfrom vaporization of the sprayed water, and controlling the castingprocess in accordance with that pressure.
 2. The method as set forth inclaim 1 the control step including throttling of the water supply forspraying, upon sudden increase of the pressure.
 3. The method as setforth in claim 1 the control of the casting process including the stepof controlling the supply of liquid steel for the casting process. 4.Apparatus for supervising the continuous casting of steel tubes whichincludes means for cooling the cast tubes in the respective interior byspraying of water, comprising: means for measuring the pressure of thesteam resulting from vaporization of the sprayed water; and means forcontrolling the casting process in accordance with that pressure. 5.Apparatus as set forth in claim 4, the means for measuring including aprobing pipe extending into the interior of the cast tube.
 6. Apparatusas set forth in claim 5, the probing pipe extending to a region adjacentan interior surface portion of the cast tube towards which water issprayed.
 7. In an apparatus for continuously casting a steel tube, thecast tube leaving a die cavity, there being means in communication withthe interior of the cast tube during the casting process; the apparatusfurther including means for spraying cooling water onto the innersurface of the cast tube, the improvement comprising: first means incommunication with the interior of the cast tube to be responsive to thepressure of developing steam in the tube; and second means operativelyconnected to the first means to retard the casting process in responseto development of pressure indicative of a crack forming in the tube. 8.In an apparatus as set forth in claim 7 the second means including meansfor controlling the flow of liquid steel into the die cavity.
 9. In anapparatus as set forth in claim 8, the means included in the secondmeans stopping flow of liquid steel into the die cavity when the steampressure exceeds a particular value.
 10. In an apparatus as set forth inclaim 7 including third means connected to the first means andresponsive to the pressure in the tube to control the flow of water forspraying the interior of the tube.
 11. In an apparatus as set forth inclaim 10 the third means throttling the flow of spray water when thepressure exceeds a danger limit.